(1) Field of the Invention
The present invention relates to a speed reduction system having a high reduction ratio. More particularly, the invention concerns a speed reduction system which utilizes a planet gear mechanism and can attain the speed reduction at a higher ratio for its size which is relatively small, and which has a high durability.
(2) Brief Description of the Prior Art
Planet gear mechanism are generally characterized in that they can be relatively small in size and yet can provide a speed reduction at relatively high ratios. However, with such mechanisms, errors in processing, if any, would become synergistically manifested during the operation, so that an extremely high precision is required to answer in the production or assembling of the mechanism: If there are errors with respect to gears or in the indexing of planet shafts, the load imposed cannot be uniformly distributed on respective planet gears and it often happens that the inter-gear meshing or engagement is excessively strong with some gears and very weak with the other, permitting to readily occur abnormal vibration, abrasion and wearing, and also a great power loss. Similarly, with the conventional speed reduction systems it has been highly likely that gears or shafts undergo irregular rotation, if slightly, whereby the durability of the system is drastically lowered.
In addition to the foregoing difficulties, conventional speed reduction systems present another problem such that since processing should be performed at a high precision in order to prevent the above-mentioned irregular engagement among the members of planet gear mechanisms, the manufacturing cost is inevitably increased. Further, the life of such conventional system is extremely short, and various difficulties are encountered when it is used under a high load condition.
A system in which a plurality of planet gear mechanisms are arranged in series so as to obtain a high reduction ratio has already been proposed. However, the structure of such conventional system is complicated and it is very difficult to assemble or disassemble this conventional system. Moreover, the system cannot be manufactured at a relatively low cost. (3) Objects of the Invention:
The present invention has been made as a result of investigations made with a view to developing a speed reduction system in which the foregoing defects involved in the conventional techniques can be eliminated.
It is therefore a primary object of the present invention to provide a speed reduction system in which the engagement between a sun gear and a planet gear is very smooth and occurrence of irregular engagements can be completely prevented, and which has a high durability and can attain a very high reduction ratio at a high transmission efficiency.
Another object of the present invention is to provide a speed reduction system which as a simple structure with a high durability and yet can be manufactured at a low cost.
Still another object of the present invention is to provide a multi-stage planetary gear speed reduction system which can be assembled or disassembled very easily and simply.